The Western Harbour Tunnel and Beaches Link tollway is expected to bypass up to 19 sets of traffic lights and cut the travel time between Brookvale and the CBD by 40 minutes. It will require the erection of six exhaust ventilation stacks for which sites have been identified, several within metres of schools.

The $14 billion price tag includes about $340 million for property acquisitions, $5 billion for the direct cost of construction, $2.3 billion for indirect costs and $5 billion for contingencies and cost escalation.

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As many as 20 houses would need to be acquired and demolished to build the tunnel, as well as 30 multi-occupancy buildings and 20 commercial buildings, most of them near exhaust stacks.

The Wenona School in North Sydney, the Anzac Park Primary School in Cammeray and the Seaforth Public School are each within 200 metres of the sites chosen for smokestacks, as are schools not identified when the Herald identified the proposed locations on Monday.

The Crows Nest TAFE is within 500 metres of the proposed Ridge Street exhaust stack in North Sydney and in 2019 will become the senior campus of Cammeraygal High. Other schools within 500 metres of proposed smokestacks include Marist College North Shore, the North Sydney Boys High School, the Cameragal Montessori School, the KU Cammeray Pre-School, the Balgowlah Boys Campus of the Northern Beaches Secondary College and the KU Bligh Park Pre-School.

Each exhaust stack, up to 35 metres high would be accompanied by a ventilation plant of between 1500 and 2500 square metres.

Premier Gladys Berejiklian said on Monday that locations for exhaust stacks "had not been finalised at all" as geotechnical and design work was still under way.

"It is way too early to make any predictions about where things are going to be," she said.

The costing document seen by Fairfax Media is titled "Final Business Case". A separate cabinet-in-confidence report includes three slightly different routes for the tollway, but only one set of locations for exhaust stacks.

Ms Berejiklian said her government had been "transparent at every level on every project because it's always in our interests to communicate as soon as we know something".

Opposition Leader Luke Foley said the government was treating the people of NSW with contempt. "Have they learnt nothing from WestConnex? Yet again, here is advanced planning for smokestacks, for a big mega-tunnel that will impact on hundreds of thousands of people and yet there's no consultation with the community."

The premier announced the Beaches Link before the March North Shore by-election. In March the government committed $77 million for geotechnical work along the route and in June a further $17.6 million for planning the route.

The previously undisclosed total of $14 billion compares with $16.8 billion for WestConnex (up from $10 billion when it was first announced) and $14.5 billion plus operational and maintenance costs for the proposed F6 Extension to the Illawarra region.

It raises questions about the capacity of the state budget to sustain all three road projects.

Asked whether $14 billion was the working price for building the Western Harbour Tunnel and Beaches Link a spokesman for roads minister Melinda Pavey said it was too early to determine a final price.

The Western Harbour Tunnel and Beaches Link was going through a process of review and market testing to provide the greatest benefit to the taxpayer.

Roads and public transport projects were not mutually exclusive.

The 36-kilometre Rouse Hill to Chatswood rail upgrade is much cheaper than the Beaches Link at $8 billion, around $230 million per kilometre.

An internal Transport for NSW memo released under the Government Information (Public Access) Act refers to a cabinet directive not to consider public transport alternatives when assessing tollway projects. The memo says the Western Harbour Tunnel and Beaches Link was not benchmarked against a public transport alternative.